Effects of obesity and acute resistance exercise on skeletal muscle angiogenic communication pathways.

Obesity (OB) impairs cell-to-cell communication signalling. Small extracellular vesicles (EVs), which include exosomes, are released by skeletal muscle and participate in cell-to-cell communication, including the regulation of angiogenesis. Resistance exercise (REx) increases muscle fibre size and capillarization. Although obesity increases muscle fibre size, there is an inadequate increase in capillarization such that capillary density is reduced. It was hypothesized that REx-induced angiogenic signalling and EV biogenesis would be lower with obesity. Sedentary lean (LN) and OB subjects (n = 8 per group) performed three sets of single-leg knee-extension REx at 80% of maximum. Muscle biopsies were obtained at rest, 15 min and 3 h postexercise and analysed for angiogenic and EV biogenesis mRNA and protein. In OB subjects, muscle fibre size was ∼20% greater and capillary density with type II fibres ∼25% lower compared with LN subjects (P < 0.001). In response to REx, the increase in VEGF mRNA (pro-angiogenic) was similar (3-fold) between groups, while thrombospondin-1 (TSP-1) mRNA (anti-angiogenic) increased ∼2.5-fold in OB subjects only (P = 0.010). miR-130a (pro-angiogenic) was ∼1.4-fold (P = 0.011) and miR-503 (anti-angiogenic) ∼1.8-fold (P = 0.017) greater in OB compared with LN subjects at all time points. In both groups, acute REx decreased the EV surface protein Alix by ∼50%, consistent with the release of exosomes (P = 0.016). Acute REx appears to induce the release of skeletal muscle small EVs independent of body mass. However, with obesity there is predominantly impaired angiogenic signalling, consistent with inadequate angiogenesis in response to basal muscle hypertrophy.